Aircraft: B767
Phase of flight: Takeoff / Launch
Anomaly: Aircraft Equipment Problem Critical

The Captain and I discussed in depth the preflight procedures; and to be extra vigilant as we proceeded through our checks due to the fact that the aircraft has been at a maintenance contract facility. The preflight went slower than normal and we both discovered that some switches were not in the normal position. The exterior preflight I conducted was also methodical; with nothing out of the ordinary. Start up; taxi out went normal; with final weight being about 240;000 pounds. Since it was such a light aircraft; we decided to conduct a flaps 15 takeoff. This discussion came up since neither of us had flown that light of an aircraft and we wanted maximum tail runway clearance. The aircraft accelerated amazingly fast and as I was scanning the engines; I looked to the airspeed indicator and as I was calling 100 knots I noticed the ECAS message 'R wing slide'; and believe I said; 'right wing slide; 100 knots'. We continued the takeoff roll based upon abort criteria in the high speed regime; and what we briefed. Takeoff; cleanup and acceleration through 3000 ft went normal. I checked the cabin pressurization gauge and it was normal; so we took a higher altitude offered by departure. Once safely climbing I asked the Captain to select the auto pilot so I could open the QRH and locate the proper procedure to conduct. During the climb to 10;000 feet; ATC cleared us to FL200; I selected 200 in the MCP and continued with the QRH. I read the QRH aloud and came to the point where a visual inspection needed to be conducted. With the autopilot on and aircraft stable; I grabbed my flashlight and went back to investigate. As I approached the right wing root area there was a very loud banging on the side of the aircraft; however I was unable to visually see anything through the passenger windows. I returned to the cockpit and advised the Captain on my findings. ATC was advised of our situation and after a few minutes ATC advised us that the slide was located within the airfield boundary. At that time we were assured that we were not 'dragging' the slide; but still we were unsure as to what was causing the banging on the side of the fuselage. ATC gave us vectors to final for a landing. We asked for Crash Fire Rescue to meet us on landing rollout to advise us of damage to aircraft. Normal approach and landing was conducted and after coming to a full stop we secured the right motor so CFR could get a close look of the area. After several minutes of inspecting for damage; CFR escorted us to the maintenance hangar. We left flaps and spoilers in the landing configuration. Post flight inspection revealed that the slide pack door was open and the remaining portion of the slide pack was hanging from the slide compartment. The side of the aircraft just aft of the wing root was black from fabric rubbing and the banging heard while airborne was from the metal air fittings beating the flap and fuselage. There was one two inch hole in the upper surface of the flap and several dimpled marks on the fuselage. The gauge on the air bottle that inflates the slide indicated zero PSI. [Report narrative contained no additional information.] B767 flight crew reported that a right overwing slide deployed at approximately 100 kts on the takeoff roll; necessitating a return to departure airport.